The correct option is D 312
Calculate the fraction of puzzle pieces to be kept in the fourth bag.
So, let's calculate the total number of pieces in first three bags.
Fraction of puzzle pieces in the first three bags = 412+312+212 (like fractions)
As the denominators of the fractions are same, the numerators can be added directly and the denominator remains same.
=(4+3+212)
=912
So, the fraction of pieces in three bags is 912.
To find the fraction of pieces in the fourth bag, subtract 912 from the total number of pieces, i.e., 1212
=1212−912 (like fractions)
As the denominators of the fractions are same, the numerators can be subtracted directly and the denominator remains same.
=12−912
=312
Hence, 312 puzzle pieces are kept in the fourth bag.